Is this flow optimal for cooling? Not an easy question to answer but more flow is always better for cooling. Either way I believe this is normal.

How does this compare to larger coolers? Larger coolers will flow about the same or faster because they have less restriction.

Would a thermostatic regulator help? Absolutely not! The cooler does it's job regardless of how it's throttled and the system was designed to operate freely above idle. Why add additional unnecessary throttling?

Yes, I have some data but my thermocouples weren't operating correctly. I'll post some more after I put in the new oil cooler.